1. Field of the Invention
The present invention relates to an information processing apparatus which executes the recording and reproducing of information for recording media such as optical disks, etc.
2. Related Art of the Invention
Various kinds of information processing apparatus using optical disks as recording media, that is, so-called optical disk drives have been developed in recent years. On these optical disk drives, information are recorded on an optical disk by applying a laser beam which are generated from a semiconductor laser oscillator, that is, a light source in an optical head to an optical disk. Further, the reflected light of the laser beam from the optical disk is received by a detector provided in the optical head and information recorded on the optical disk is read by converting this laser beam into electric signals.
On the optical disk drive, when recording information, new information may be written inadvertently on adjacent tracks where other information have been already written due to tracking error etc. caused by external shocks. In other words, there was a possibility for destructing already written information by overwriting new information on them.
In the optical disk drive, it was necessary to determine whether there were already recorded information or not when the information were read out from the optical disk.
As disclosed in U.S. Pat. No. 5,101,396 (issued on Mar. 31, 1992), it was a practice so far made to determine whether there were already recorded information by using the upper end detection signal of information signal read out of the optical disk.
However, as circuits for making the determination, two circuits: an upper detection circuit and a binarization circuit were needed. As a result, the entire circuits of the optical disk drive were so complicated.